1. Field of the Invention
The present invention relates to an optical system having a wide angle of view and a compact size, an image pickup device comprising the optical system and a digital apparatus comprising the image pickup device (for example, monitor cameras such as a security camera and an in-vehicle camera).
2. Description of the Related Art
When cameras having a wide angle of view in photographing are used, an image can be picked up in a wider range and with a fewer number of cameras. Therefore, a wide-angle optical system having a wide angle of view (wide angle lens) is preferably used as a lens installed in a security camera and an in-vehicle camera so that a wider photographing range can be obtained.
For example, the in-vehicle camera (used as a rear-view monitor installed in a vehicle or the like) is required not only to have the wide angle of view but also to have a compact size in view of such a practical aspect as not blocking a driver's view and such an aesthetical aspect as not undermining a design of the vehicle.
As an example of the wide-angle optical system, a wide-angle optical system comprising six components: a first lens group having a negative optical power; a second lens group having the negative optical power; a third lens group having a positive optical power; a fourth lens group having the negative optical power; a fifth lens group having the positive optical power; and a sixth lens group having the positive optical power, which are serially disposed from an object side, is recited in No. H05-264897, No. H11-249009 and No. 2000-352665 of the Publication of the Unexamined Japanese Patent Applications.
However, a maximum angle of view is such a small degree as approximately 60-65° and an entire optical length has such a lengthy dimension as at least 25 mm in the wide-angle optical systems recited in H05-264897.and No. H11-249009. In the wide-angle optical system recited in No. 2000-352665, the maximum angle of view exceeds 80°, however, a wider angle of view is desirably obtained when used as the monitor camera. Further, the wide-angle optical system recited in No. 2000-352665 has the entire optical length of such a lengthy dimension as approximately 25 mm in the same manner as in the wide-angle optical systems recited in H05-264897 and No. H11-249009, and is necessarily further downsized to be installed in digital apparatuses typified by the monitor camera such as the in-vehicle camera and a mobile telephone.